/Engine/Source/Runtime/Core/Public/Math/UnrealMathUtility.h
Returns a smooth Hermite interpolation between 0 and 1 for the value X (where X ranges between A and B) Clamped to 0 for X <= A and 1 for X >= B.
Smoothed value between 0 and 1
template<typename T> static constexpr T SmoothStep ( T A, T B, T X )